<tex> regula sigma 21: (n - 1)! \equiv -1(\text{mod }n)</tex>
<tex> regula sigma 22: \binom{m}{n} = \prod^{k}_{1}{\binom{m_i}{n_i}} \text{  (mod p)}</tex>
<tex> regula sigma 23: (\sum^{n}_{1}{(a_k + b_k) ^ p})^{\frac{1}{p}} \leq (\sum^{n}_{1}{a_k^p}) ^{\frac{1}{p}} + (\sum^{n}_{1}{b_k^p}) ^{\frac{1}{p}} </tex>

<tex> regula sigma 24: \sum^{n}_{1}{a_i b_i} \leq (\sum^{n}_{1}a_i^p)^{\frac{1}{p}} + (\sum^{n}_{1}b_i^q)^{\frac{1}{q}} </tex>
<tex> regula sigma 25: \frac{f(a) - f(b)}{g(a) - g(b)} = \frac{f(c)}{g(c)}</tex>
<tex> regula sigma : </tex>
<tex> regula sigma : </tex>
<tex> regula sigma : </tex>
<tex> regula sigma : </tex>

<tex> regula sigma 24: \sum^{n}_{1}{a_i b_i} \leq (\sum^{n}_{1}a_i^p)^{\frac{1}{p}} + (\sum^{n}_{1}b_i^q)^{\frac{1}{q}} </tex>